JP2011093204A - Thermal recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording medium that is superior in color developing sensitivity, preservability (particularly, plasticizer resistance), and heat resistance while preventing color fading of a color developing part and deterioration in ground color. <P>SOLUTION: The thermal recording medium is configured to provide a thermal recording layer, containing a colorless or pale-colored electron-donating leuco dye, an electron-accepting color-developing agent, and a sensitizer, on a support. The thermal recording layer contains the sensitizer in which the particle-size distribution (the volumetric basis) of fine particles, measured by a laser diffraction particle size analyzer, is ≤0.6 μm by 50% diameter and ≤3.0 μm by 90% diameter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material that utilizes a color development reaction caused by heat between a colorless or light-colored basic leuco dye and an electron-accepting developer. The present invention relates to a heat-sensitive recording material excellent in plasticizer resistance) and heat resistance, in which a colored portion is not easily faded and the ground color does not deteriorate.

Generally, a colorless or light-colored electron-donating leuco dye (hereinafter sometimes simply referred to as “dye”) and an electron-accepting developer that reacts with the dye when heated (hereinafter simply referred to as “developer”). In other words, thermal recording materials having a thermosensitive color-forming layer mainly composed of the above are widely put into practical use. In order to perform recording on this thermal recording medium, a thermal printer or the like with a built-in thermal head is used. Compared with other recording systems that have been put to practical use, this thermal recording system has no noise during recording, does not require development and fixing, is maintenance-free, is relatively inexpensive, and is compact. The developed color is very clear, and it is widely used in facsimiles, computer terminal printers, automatic ticket vending machines, measuring recorders, handy terminals used outdoors, and the like. As a use of this thermal recording medium, in addition to the above-mentioned output paper of various devices, it has come to be used in fields such as cash voucher paper that requires high storage stability.
As these devices are diversified and have higher performance, the required quality for thermal recording media has become higher. In particular, when heat-sensitive recording media are used for various tickets, receipts, labels, bank ATMs, gas and electricity meter readings, and car vouchers, etc. Therefore, there is a demand for plasticizer resistance that does not cause a problem in the readability of the printed part even when stored in a state of being stored. In order to improve color development sensitivity and provide image storability, for example, a specific developer and a sensitizer are used in combination to increase sensitivity, and a specific stabilizer is used to improve storability. Further, there is disclosed a heat-sensitive recording material (Patent Document 1) and a heat-sensitive recording material (Patent Document 2) having improved color development sensitivity and storage stability by using a hydroxybenzenesulfonanilide compound as a developer. In general, the sensitivity of each material is improved by atomizing a sensitizer, a dye, a developer or a stabilizer to improve the reactivity of each material.

JP 2005-262819 A Special registration 04161778

However, as thermal recording media are increasingly used in applications that are used in harsh environments such as gold vouchers, color sensitivity and image area storability that are higher than conventional ones are required. The thermal recording material of Document 1 is at a level that requires improvement in both the color development sensitivity and the storage stability of the image area. The thermal recording medium of Patent Document 2 has good color development sensitivity, but the storage quality of the image area is required. It is a level that does not reach. In addition, when various materials are atomized, the color development sensitivity is improved, but the heat resistance is lowered, and a new problem arises that the background stain of the white paper portion occurs.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat-sensitive recording material that has excellent color development sensitivity, and has good storage stability (plasticizer resistance) in an image area and background stain (heat resistance) in a white paper area.

As a result of intensive studies, the present inventors have found that a thermal recording material excellent in color development sensitivity, plasticizer resistance and heat resistance can be obtained by atomizing a specific sensitizer into a specific particle size distribution, The present invention has been completed.
That is, the present invention is a heat-sensitive recording material provided with a heat-sensitive recording layer containing a colorless or light-colored dye, a developer and a sensitizer on a support, and the heat-sensitive recording layer has a laser diffraction particle size distribution. A thermal recording material comprising a sensitizer whose particle size distribution (volume basis) measured by a measuring apparatus is 50 μm diameter and 0.6 μm or less, and 90% diameter and 3.0 μm or less. In particular, it has been found that an excellent effect is exhibited by using a sensitizer of the following general formula (Chemical Formula 1) to General Formula (Chemical Formula 6).

  According to the present invention, it is possible to obtain a heat-sensitive recording material that has excellent color development sensitivity and good storage stability (plasticizer resistance) in the image area and background stain (heat resistance) in the white paper area.

The heat-sensitive recording material of the present invention comprises a dispersion of at least one sensitizer of the following general formulas (Chemical Formula 1) to (Chemical Formula 6), a dye and a developer, a binder, a filler, etc. Other necessary additives may be added and mixed to prepare a heat-sensitive recording layer coating solution, which may be applied and dried on a substrate to form a heat-sensitive recording layer.

In the present invention, the particle size distribution of the general formula (Chemical Formula 1) to the general formula (Chemical Formula 6) is 50% from the small particle diameter side (hereinafter also referred to as “50% diameter” or simply “average particle diameter”). When the particle diameter at 90% (hereinafter referred to as “90% diameter”) is 3.0 μm or less, the excellent effect can be exhibited. The particle size distribution of the sensitizer is a value obtained by measuring the volume-based cumulative particle size distribution frequency with a laser diffraction particle size distribution measuring apparatus. Preferably, the average particle diameter is 0.3 μm to 0.6 μm, and the 90% diameter is 0.5 μm to 1.5 μm, and more preferably the average particle diameter is 0.3 μm to 0.5 μm and 90%. The diameter is 0.6 μm to 1.0 μm.
In the present invention, the general formula (Chemical Formula 1) to the general formula (Chemical Formula 6) can improve the color development sensitivity, plasticizer resistance, and heat resistance by having the above particle size distribution.

The reason is not clear, but is presumed as follows.
In general, a sensitizer is used in a thermal recording material to improve color development sensitivity, and the color development mechanism is usually the sensitizer having the lowest melting point among dyes, color developers and sensitizers first. After melting, the dye and the developer dissolve in the melted sensitizer, and the dye and the developer react at the molecular level to obtain color. In the present invention, the sensitizer represented by the general formula (Chemical Formula 1) to the general formula (Chemical Formula 6) is atomized into the above particle size distribution, so that the meltability of the sensitizer is increased and the dye which is a color developing component Further, it is considered that the contact frequency with the developer increases and the color development sensitivity is greatly improved. In addition, the sensitizer whose particle size distribution is adjusted to the above range has a very small particle size that adversely affects heat resistance and a ratio of a very large particle size that adversely affects the color development sensitivity, and thus is good. It is presumed that a color-sensitive and heat-resistant thermal recording material can be obtained. Further, it is presumed that the plasticizer resistance of the image area is also improved by adjusting the particle size distribution of the sensitizer to the above range.

  In the present invention, the general formula (Chemical Formula 1) to the general formula (Chemical Formula 6) may be used in combination as long as the desired effects are not inhibited. In addition to the above, other conventionally known sensitizers are used in combination. May be. The particle size of such a sensitizer is not particularly limited, and may be atomized in the same manner as in the general formula (Formula 1) to the general formula (Formula 6). When such a sensitizer is used in combination, the ratio of the other sensitizers to the entire sensitizer to be used is particularly limited as long as it is appropriately adjusted within a range not inhibiting the desired effect. However, when the entire sensitizer is 100% by weight, the total amount of the sensitizer represented by the general formula (Chemical Formula 1) to the general formula (Chemical Formula 6) is 50 to 100% by weight, preferably 60 to 100%. It is desirable to use so that it may become weight%.

  Examples of such sensitizers include stearamide, methylolamide, ethylenebisamide, montanic acid wax, palmitic acid amide, polyethylene wax, p-benzylbiphenyl, β-benzyloxynaphthalene, 4-biphenyl-p-tolyl ether. M-terphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, bis [2- (4-methoxy-phenoxy) ethyl] ether, methyl p-nitrobenzoate, Dibenzyl oxalate, di (p-chlorobenzyl) oxalate, di (p-methylbenzyl) oxalate, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene 1-hydroxy-2-naphthoic acid phenyl ester, 4- (m-methylphenoxymethyl) biphenyl, orthotoluenesulfonamide, paratoluenesulfonamide, 1,2-diphenoxyethane, 1,2-di (3-methyl Phenoxy) ethane and methylbiphenyl ketone can be exemplified, but not limited thereto. These sensitizers may be used alone or in combination of two or more.

In the present invention, the method for adjusting the sensitizer represented by the general formula (Chemical Formula 1) to the general formula (Chemical Formula 6) to a specific particle size distribution is not particularly limited. There is a tendency to thicken or agglomerate during atomization, and it is difficult to obtain a sharp particle size distribution. Therefore, microbeads (media) (hereinafter sometimes simply referred to as “beads”) are used as grinding media, wet milled by a bead mill, and separated into beads and dispersion by the action of centrifugal force, and then discharged from the bead mill. It is preferable to use a machine.

In addition, the pulverizer to be used is not particularly limited, and examples thereof include a screen type pulverizer, a gap type pulverizer, and a pulverizer using a centrifugal separation method. It is desirable to use a crusher using a centrifugal separation system for the mechanism. The pulverizer is a wet type pulverizer having a mechanism for separating the dispersion liquid and the medium using centrifugal force, which is greatly different from the screen type and gap type used in the conventional pulverizer.

In the present invention, the particle diameter of the medium to be used may be appropriately selected depending on the desired particle diameter to be obtained, but in order to promote a sharp particle size distribution and atomization, a range of 0.03 to 0.5 mm diameter. The beads are preferably selected, and the material is preferably selected from glass, zirconia, and alumina. If the bead particle size exceeds 0.5 mm, the impact force per bead used for grinding (proportional to the weight of the bead, and the bead weight is proportional to the cube of the bead diameter) becomes excessive, and the sensitizer The particle surface is damaged, and the particle surface is activated unnecessarily. As a result, thickening and aggregation occur due to the interaction between the particles, and coarse particles are generated, making it difficult to atomize.
In the present invention, the apparent filling rate of the bead particles in the grinding chamber is preferably 30 to 95% by volume, more preferably 40 to 90% by volume. By making the filling rate of the bead particles in the above range, the sensitizer atomization efficiency is good and short pass can be prevented.

In the present invention, it is desirable that the processing temperature when pulverizing the sensitizer is 50 ° C. or lower. When processed at 50 ° C. or higher, re-aggregation or denaturation is caused by heat, so there is a concern that the color development sensitivity is lowered. This reduction in color development sensitivity due to aggregation or the like can be evaluated with a 90% diameter, and is preferably about twice or less than the target average particle diameter (50% diameter). In addition, when the dispersion is mixed at 50 ° C. or higher, the mixed paint is colored. Therefore, it is necessary to use the solution after cooling it to 50 ° C. or lower, which reduces the production efficiency.

The method for cooling the dispersion is not particularly limited, but a method of cooling by circulating a cooling medium in the jacket portion of the grinding chamber is simple. The temperature control method is not particularly limited, but when the cooling medium is circulated, the flow rate and temperature may be controlled. The method automatically measures the temperature of the dispersion using a sensor and controls the value. Alternatively, simply determine the conditions for measuring the temperature of the dispersion at the highest dispersion outlet while changing the cooling medium, flow rate, and temperature to bring the desired dispersion temperature. Also good. A normal cooling medium such as water or ethylene glycol can be used as the cooling medium.
Before the atomization operation, a coarse dispersion operation is performed as a pretreatment, such as a ball mill, an attritor, a sand mill, a sand grinder, a grain mill, a pearl mill, a matter mill, an anil mill, a coball mill, a tower mill, a dynamic mill, an OB mill, an apex mill, and an SC mill. There are various deformation types and names such as a three-roll mill, and among these, there are many types of modifications, but a necessary coarse dispersion treatment may be performed as appropriate. Further, the atomization operation may be a continuous method by connecting pulverizers in series, or a method of circulating and passing a plurality of times. Specific examples of a pulverizer for centrifuging a dispersion liquid and beads as a preferable pulverizer to be used include Super Apex Mill (SAM-05 type, SAM-1 type, SAM-2 type, manufactured by Kotobuki Kogyo Co., Ltd.). , SAM-5 type, SAM-10 type, SAM-30 type), Ultra Apex mill (UAM-015 type, UAM-05 type, UAM-1 type, UAM-2 type, UAM-5 type, UAM-10 type) , UAM-30 type), MSC mill (MSC100, MSC150, MSC220) manufactured by Mitsui Mining Co., Ltd .. Since these pulverizers are screenless, rough dispersion treatment for the purpose of preventing clogging and biting can be omitted. In addition, Star Mill LMZ (LMZ06, LMZ2, LMZ4, LMZ10, LMZ25, LMZ60) and Star Mill ZRS (ZRS2, ZRS4, ZRS10) manufactured by Ashizawa Finetech Co., Ltd., which use both centrifugal separation and a screen mechanism to separate the dispersion and beads. However, it is not limited to these as long as atomization within the particle size distribution range is possible. Specific examples of the gap type include bead mills (SC100, SC220, etc.) manufactured by Mitsui Mining Co., Ltd., but are not limited thereto.

  As a dispersion medium used when dispersing the sensitizer, an aqueous solution of a water-soluble polymer compound is generally used. For example, polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / In addition to water-soluble polymers such as methacrylic acid terpolymers, styrene / maleic anhydride copolymer alkali salts, isobutylene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin and casein, polyacetic acid Vinyl, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate Emulsion and styrene / butadiene copolymers such as polymers, such as latex, such as styrene / butadiene / acrylic copolymer may also be mentioned.

When these dispersants (solid content) are used in an amount of 0.01 to 1.0 part by weight with respect to 1 part by weight of the object to be dispersed, it is advantageous for finer particles, improved dispersibility, and stability of the dispersion. This is preferable. If the amount is too small, aggregation is caused and the stability of the dispersion is poor. On the other hand, when the amount is too large, quality is adversely affected, such as a reduction in sensitivity due to a desensitizing action, which is not preferable. The density | concentration of the dispersion target object in a dispersion liquid is about 20 to 70 weight% normally.
Using such a material, a sensitizer dispersion is prepared and atomized under the above conditions. When a pulverizer that centrifuges the dispersion and beads is not used, a ball mill, an attritor, a sand mill, a sand grinder, a grain mill, a pearl mill, a matter mill, an aniler mill, a coball mill, a tower mill, a dynamic mill, an OB mill, an apex mill, three A conventional crusher such as the present roll mill can be used.
In addition, you may atomize other components (a dye, a color developer, a stabilizer, another sensitizer, etc.) similarly.

As the developer used in the present invention, any known developer in the pressure-sensitive recording material field or the thermal recording paper field can be used, and is not particularly limited. Moreover, you may use these together in the range which does not inhibit the desired effect with respect to the said subject. The particle size of such a developer is not particularly limited and is generally about 0.3 to 1.0 μm in average particle size, and may be atomized in the same manner as the sensitizer.

  Examples of such developers include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2 , 2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4-hydroxybenzenesulfonanilide, JP-A-8-59603 Aminobenzenesulfonamide derivatives, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, bis ( p-hydroxyphenyl) Acid methyl, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α -Methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2′-thiobis ( 4-tert-octylphenol), phenolic compounds such as diphenylsulfone cross-linking compounds described in International Publication WO 97/16420, 4,4′-bis (3- (phenoxycarbonylamino) methylphenylureido) diphenylsulfone (Asahi Kasei Corporation) Product name: UU), compounds described in International Publication WO02 / 081229 or JP2002-301873 (Japan) Soda Co., Ltd. trade names D-102, D-100), compounds described in Japanese Patent Nos. 34566792 and 36127746, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, p-chlorobenzoic acid, gallic acid Stearyl acid, zinc bis [4- (n-octyloxycarbonylamino) salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyl Oxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid aromatic carboxylic acid, and zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel of these aromatic carboxylic acids Salts with polyvalent metal salts such as zinc thiocyanate antipyrine complex, terephthalate Examples include complex zinc salts of aldehyde and other aromatic carboxylic acids. These may use 1 type or may use several types together.

As the dye used in the present invention, all known dyes in the pressure-sensitive recording material field or the thermal recording paper field can be used, and are not particularly limited, but are triphenyl compounds, fluoran compounds, fluorene compounds. , Divinyl compounds and the like are preferable. In addition, you may use these together in the range which does not inhibit the desired effect with respect to the said subject. The particle size of such a dye is not particularly limited and is generally about 0.2 to 1.0 μm in average particle size, and may be atomized in the same manner as the sensitizer.

Specific examples of typical dyes are shown below.
<Triphenylmethane leuco dye>
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide [also known as crystal violet lactone]; 3,3-bis (p-dimethylaminophenyl) phthalide; [also known as malachite green lactone]

<Fluoran leuco dye>
3-diethylamino-6-methylfluorane; 3-diethylamino-6-methyl-7-anilinofluorane; 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane; 3-diethylamino- 6-methyl-7-chlorofluorane; 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane; 3-diethylamino-6-methyl-7- (o-chloroanilino) fluorane; Diethylamino-6-methyl-7- (p-chloroanilino) fluorane; 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluorane; 3-diethylamino-6-methyl-7- (m-methylanilino) fluorane 3-diethylamino-6-methyl-7-n-octylanilinofluorane; 3-diethylamino-6-methyl-7-n-octylaminofluorane; 3-diethylamino-6-methyl-7-benzylaminofluorane; 3-diethylamino-6-methyl-7-dibenzylaminofluorane; 3-diethylamino-6-chloro-7-anilinofluorane; 3-diethylamino-6-chloro-7-p-methylanilinofluorane; 3-diethylamino-6 3-Ethoxyethyl-7-anilinofluorane; 3-diethylamino-7-methylfluorane; 3-diethylamino-7-chlorofluorane; 3-diethylamino-7- (m-trifluoromethylanilino) fluorane; Diethylamino-7- (o-chloroanilino) fluorane; 3-diethyla 3-diethylamino-7- (o-fluoroanilino) fluorane; 3-diethylamino-benzo [a] fluorane; 3-diethylamino-benzo [c] fluorane; 3-dibutylamino 3-dibutylamino-6-methyl-7-anilinofluorane; 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluorane; 3-dibutylamino- 6-methyl-7- (o-chloroanilino) fluorane; 3-dibutylamino-6-methyl-7- (p-chloroanilino) fluorane; 3-dibutylamino-6-methyl-7- (o-fluoroanilino) fluorane 3-dibutylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane 3-dibutylamino-6-methyl-chlorofluorane; 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane; 3-dibutylamino-6-chloro-7-anilinofluorane; 3-dibutylamino -6-methyl-7-p-methylanilinofluorane; 3-dibutylamino-7- (o-chloroanilino) fluorane; 3-dibutylamino-7- (o-fluoroanilino) fluorane; 3-di-n -Pentylamino-6-methyl-7-anilinofluorane; 3-di-n-pentylamino-6-methyl-7- (p-chloroanilino) fluorane; 3-di-n-pentylamino-7- (m -Trifluoromethylanilino) fluorane; 3-di-n-pentylamino-6-chloro-7-anilinofluorane; 3-di-n-pentyl Mino-7- (p-chloroanilino) fluorane; 3-pyrrolidino-6-methyl-7-anilinofluorane; 3-piperidino-6-methyl-7-anilinofluorane; 3- (N-methyl-N- Propylamino) -6-methyl-7-anilinofluorane; 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-cyclohexylamino) ) -6-Methyl-7-anilinofluorane; 3- (N-ethyl-N-xylamino) -6-methyl-7- (p-chloroanilino) fluorane; 3- (N-ethyl-p-toludino)- 6-methyl-7-anilinofluorane; 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-isoamido) Amino) -6-chloro-7-anilinofluorane; 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-isobutyl) Amino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-ethoxypropylamino) -6-methyl-7-anilinofluorane; 3-cyclohexylamino-6-chlorofluorane; 2- (4-oxahexyl) -3-dimethylamino-6-methyl-7-anilinofluorane; 2- (4-oxahexyl) -3-diethylamino-6-methyl-7-anilinofluorane; 2 -(4-oxahexyl) -3-dipropylamino-6-methyl-7-anilinofluorane; 2-methyl-6-p- (p-dimethylaminophenyl) aminoani 2-methoxy-6-p- (p-dimethylaminophenyl) aminoanilinofluorane; 2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane; Chloro-6-p- (p-dimethylaminophenyl) aminoanilinofluorane; 2-nitro-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 2-amino-6-p- (p- 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 2-phenyl-6-methyl-6-p- (p-phenylaminophenyl) aminoani Linofluorane; 2-benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane; 2-hydroxy-6-p- (p-phenylaminophenyl) aminoanilinofluorane; 3-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane; 3-diethylamino-6-p- (P-diethylaminophenyl) aminoanilinofluorane; 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane; 2,4-dimethyl-6-[(4-dimethylamino) anilino] -Fluoran

<Fluorene leuco dye>
3,6,6′-tris (dimethylamino) spiro [fluorene-9,3′-phthalide]; 3,6,6′-tris (diethylamino) spiro [fluorene-9,3′-phthalide]

<Divinyl leuco dye>
3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide; 3,3-bis- [2- (P-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide; 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ) Ethylene-2-yl] -4,5,6,7-tetrabromophthalide; 3,3-bis- [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2- Yl] -4,5,6,7-tetrachlorophthalide

<Others>
3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide; 3- (4-diethylamino-2-ethoxyphenyl) -3- ( 1-octyl-2-methylindol-3-yl) -4-azaphthalide; 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 3, 3-bis (1-ethyl-2-methylindol-3-yl) phthalide; 3,6-bis (diethylamino) fluorane-γ- (3′-nitro) anilinolactam; 3,6 Bis (diethylamino) fluorane-γ- (4′-nitro) anilinolactam; 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethyla Nophenyl) -ethenyl] -2,2-dinitrileethane; 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2- β-naphthoylethane; 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-diacetylethane; bis- [2, 2,2 ′, 2′-tetrakis- (p-dimethylaminophenyl) -ethenyl] -methylmalonic acid dimethyl ester

In the heat-sensitive recording layer of the present invention, pigments, adhesives (binders), stabilizers and the like may be used as other components.
Examples of the pigment used in the present invention include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide.

  As the binder, those generally known as adhesives for heat-sensitive recording layers can be used as long as the desired effects of the present invention are not impaired. Specifically, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxy Cellulose derivatives such as methylcellulose, ethylcellulose, acetylcellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyvinyl butyllar, Examples of polystyrene and their copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, coumaro resins It can be. These polymer substances are used by dissolving in water, alcohol, ketone, ester, hydrocarbon, or other solvents, and are used in the form of emulsification or paste dispersion in water or other media to achieve the required quality. It is also possible to use it together.

  In addition, 4,4′-butylidene (6-tert-butyl-3-methylphenol), 2,2 ′ is used as a stabilizer that imparts oil resistance and the like of recorded images within a range that does not impair the desired effect on the above-described problems. -Di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1, It is also possible to add 3-tris (2-methyl-4-hydroxy-5-t-butylphenylbutane, 4-benzyloxy-4 ′-(2,3-epoxy-2-methylpropoxy) diphenylsulfone epoxy resin, etc. it can.

  In addition to the above materials, lubricants such as waxes, benzophenone and triazole UV absorbers, water-resistant agents such as glyoxal, dispersants, antifoaming agents, phenolic antioxidants, fluorescent dyes, etc. are used. can do.

  The kind and amount of the sensitizer, dye, developer, stabilizer and other various components used in the heat-sensitive recording material of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. However, it is usually preferred that the sensitizer is used in an amount of about 0.5 to 10 parts by weight with respect to 1 part by weight of the dye. The developer is preferably used in an amount of 0.5 to 10 parts by weight and the pigment is used in an amount of about 0.5 to 10 parts by weight with respect to 1 part by weight of the dye. About another component, a suitable quantity can be used in the range which does not inhibit the effect of this invention.

The heat-sensitive recording material of the present invention is prepared by, for example, mixing a dispersion liquid in which a sensitizer, a dye and a developer are dispersed together with a binder, and other necessary additives such as pigments, and preparing a heat-sensitive recording layer coating liquid. It can be produced by coating and drying on a substrate (support) to form a thermosensitive recording layer.
As the solvent used in the coating solution, water, alcohol, or the like can be used, and the solid content of the coating solution is about 10 to 50% by weight.
As the support, paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, non-woven fabric and the like can be used. Moreover, you may use the composite sheet which combined these as a support body.
A sensitizer, a dye, a developer, and materials to be added as needed are dispersed until a particle size of several μm or less is obtained by a pulverizer such as a ball mill, an attritor, a sand glider, or an appropriate emulsifier. Accordingly, various additive materials are added to obtain a heat-sensitive recording layer coating solution. As described above, the sensitizer is preferably atomized using a pulverizer that centrifuges the dispersion and the beads.
The means for applying the heat-sensitive recording layer coating liquid on the support is not particularly limited, and can be applied according to a well-known conventional technique. For example, an off-machine coating machine or an on-machine coating machine equipped with various coaters such as an air knife coater, a rod blade coater, a bill blade coater, a roll coater, and a curtain coater is appropriately selected and used.
The coating amount of the thermosensitive recording layer is not particularly limited, and is usually ² to 12 g / m ² by dry weight.

  In addition, an overcoat layer is provided on the heat-sensitive recording layer for the purpose of enhancing the storage stability, and an undercoat layer such as a polymer substance containing a pigment or an organic filler is provided under the heat-sensitive recording layer for the purpose of enhancing the color development sensitivity. Or may be provided. It is also possible to provide a backcoat layer on the opposite side of the support from the thermosensitive recording layer to correct the back barrier and curl. Further, various known techniques in the heat-sensitive recording material field, such as applying a smoothing process such as supercalendering after coating each layer, can be added as appropriate. Furthermore, it can be processed into various forms such as providing a pressure-sensitive adhesive layer and release paper on the surface of the support opposite to the heat-sensitive recording layer to form a label.

  The following examples illustrate the invention but are not intended to limit the invention. In each example, “parts” means “parts by weight” unless otherwise specified.

その結果、下記に示す粒径の増感剤分散液を得た。
粒径はレーザー回折式粒度分布測定装置（マルバーン社製、マスターサイザーＳ）を用いて測定した。得られた増感剤分散液の分散粒子の５０％径は０．５１μｍ、９０％径は１．３８μｍであった。 Example 1
The sensitizer is a zirconia having a diameter of 0.3 mm using a bead mill (ultra apex mill UAM-015 type manufactured by Kotobuki Industries Co., Ltd.) that makes a dispersion having the following composition in advance and centrifuges the medium and the dispersion. Filling rate of beads 65% (pulverizer volume 0.17 L), rotor peripheral speed 12 m / sec, flow rate 10 L / Hr (flow rate / pulverizer volume = 59: the larger this value, the larger the flow rate relative to the pulverizer scale) Then, the wet pulverization was performed until the residence time (the time during which the dispersion per unit volume was ground in the pulverizer) was 5 minutes.
The normal operation was performed by changing the cooling medium, temperature and flow rate, and the conditions under which the dispersion temperature measured at the dispersion outlet at which the temperature was highest during the dispersion treatment were around 40 ° C. were determined as follows.
Cooling medium: ethylene glycol Cooling medium temperature: -2 ° C
Flow rate (circulation method): 15 L / min
<Dispersion of sensitizer (Chemical Formula 1)>
1,2-bis (3-methylphenoxy) ethane General formula (Formula 1)
(Product name: KS-232, manufactured by Sanko Co., Ltd.) 6.0 parts 10% polyvinyl alcohol aqueous solution 18.8 parts water 11.2 parts

As a result, a sensitizer dispersion having the particle size shown below was obtained.
The particle size was measured using a laser diffraction type particle size distribution analyzer (manufactured by Malvern, Mastersizer S). The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.51 μm, and the 90% diameter was 1.38 μm.

For each material of the dye and the developer, a dispersion having the following composition was prepared in advance, and wet grinding was performed with a sand grinder until the average particle size became 0.5 μm.

<Dye dispersion>
3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd., trade name: ODB-2) 3.0 parts 10% aqueous polyvinyl alcohol solution 6.9 parts water 3.9 parts
<Developer dispersion>
Phenol formaldehyde oligomer (manufactured by API Corporation, trade name JKY-224) 6.0 parts 10% polyvinyl alcohol aqueous solution 18.8 parts water 11.2 parts

Next, the following compositions were mixed to obtain a thermal recording layer coating solution. This coating solution is applied and dried on a high-quality paper having a basis weight of 50 g / m ^{2 so} that the coating amount after drying becomes 6 g / m ^2, and processed so that the Beck smoothness becomes 200 to 600 seconds with a super calendar, A heat-sensitive recording material was obtained.
Dye dispersion 13.8 parts Developer dispersion 36.0 parts Sensitizer dispersion 36.0 parts

Silica (made by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P537) 25% dispersion
13.0 parts calcium carbonate (trade name: Tunex E, manufactured by Shiraishi Calcium Co.) 50% dispersion
13.0 parts Zinc stearate 30% dispersion 6.7 parts

Example 2
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the residence time was 15 minutes. The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.40 μm, and the 90% diameter was 0.67 μm.

Example 3
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 0.5 mm diameter zirconia beads were used and the residence time was 15 minutes. The dispersed particles of the obtained sensitizer dispersion had a 50% size of 0.57 μm and a 90% size of 1.45 μm.

Example 4
A heat-sensitive recording material was produced in the same manner as in Example 1 except that 1,2-bis (3-methylphenoxy) ethane was changed to the following general formula (Formula 2). The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.51 μm, and the 90% diameter was 1.38 μm.

Example 5
A heat-sensitive recording material was produced in the same manner as in Example 1 except that 1,2-bis (3-methylphenoxy) ethane was changed to the following general formula (Formula 3). The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.51 μm, and the 90% diameter was 1.38 μm.

Example 6
A heat-sensitive recording material was produced in the same manner as in Example 1 except that 1,2-bis (3-methylphenoxy) ethane was changed to the following general formula (Formula 4). The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.51 μm, and the 90% diameter was 1.38 μm.

Example 7
A heat-sensitive recording material was produced in the same manner as in Example 1 except that 1,2-bis (3-methylphenoxy) ethane was changed to the following general formula (Formula 5). The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.51 μm, and the 90% diameter was 1.38 μm.

Example 8
A heat-sensitive recording material was produced in the same manner as in Example 1 except that 1,2-bis (3-methylphenoxy) ethane was changed to the following general formula (Formula 6). The 50% diameter of the dispersed particles of the obtained sensitizer dispersion was 0.51 μm, and the 90% diameter was 1.38 μm.

Comparative Example 1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 1.0 mm diameter zirconia beads were used. The dispersed particles of the obtained sensitizer dispersion had a 50% diameter of 0.65 μm and a 90% diameter of 3.15 μm.

Comparative Example 2
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the residence time was changed to 2 minutes. The dispersed particles of the obtained sensitizer dispersion had a 50% diameter of 0.63 μm and a 90% diameter of 3.14 μm.

The following evaluation tests were performed on the heat-sensitive recording materials obtained in the above examples and comparative examples.
[Color development sensitivity]
Using TH-PMD manufactured by Okura Electric Co., Ltd., printing was performed on the created thermal recording medium at an applied energy of 0.25 and 0.34 mJ / dot. The image density after printing and after the quality test was measured with a Macbeth densitometer (RD-914, using an amber filter).
[Plasticizer resistance] (Image residual ratio)
A heat-sensitive recording medium printed with PVC-wrap (Mitsui Toatsu, High Wrap KMA) once wrapped around a paper tube, and printed using Okura Electric's TH-PMD with an applied energy of 0.42 mJ / dot. The sample with the vinyl wrap wrapped in triplicate was left to stand for 2 hours in an environment of 23 ° C., and the image density of the recording area was measured with a Macbeth densitometer. Calculated.
Image residual ratio (%) = density after test / density before test × 100
[Heat resistance] (background density)
After pressing the thermosensitive recording surface against an 80 ° C. hot plate for 5 seconds, the color density of the background portion was measured with a Macbeth densitometer.

The evaluation results are shown in the table below.

  As is clear from the comparison between Examples 1 to 8 and Comparative Examples 1 and 2, the thermal recording material of the present invention using the general formulas (Chemical Formula 1) to (Chemical Formula 6) having a specific particle size distribution as a sensitizer. Is excellent in color development sensitivity, plasticizer resistance and heat resistance.

Claims (8)

A heat-sensitive recording material provided with a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye, an electron-accepting developer and a sensitizer on a support, the heat-sensitive recording layer having a laser diffraction particle size A heat-sensitive recording material comprising a sensitizer whose particle size distribution (volume basis) measured by a distribution measuring apparatus is 50 μm diameter and 0.6 μm or less and 90% diameter and 3.0 μm or less. .
The heat-sensitive recording material according to claim 1, wherein the sensitizer is represented by the following general formula (Formula 1).

The heat-sensitive recording material according to claim 1, wherein the sensitizer is represented by the following general formula (Formula 2).

The heat-sensitive recording material according to claim 1, wherein the sensitizer is represented by the following general formula (Formula 3).

The heat-sensitive recording material according to claim 1, wherein the sensitizer is represented by the following general formula (Formula 4).

The heat-sensitive recording material according to claim 1, wherein the sensitizer is represented by the following general formula (Formula 5).

The heat-sensitive recording material according to claim 1, wherein the sensitizer is represented by the following general formula (Formula 6).

The heat sensitizer according to claim 1, wherein the sensitizer is wet pulverized with a pulverizing medium in a bead mill, separated into a medium and a dispersion by the action of centrifugal force, and discharged from the bead mill. Recorded body.